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A likely candidate of type Ia supernova progenitors: the X-ray pulsating companion of the hot subdwarf HD 49798

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Research in Astronomy and Astrophysics 2010年第7期10卷 681-688页

作者： Bo Wang zhan-wen Han National Astronomical Observatories / Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

HD 49798 is a hydrogen depleted subdwarf 06 star and has an X-ray pulsating companion （RX J0648.0-4418）. The X-ray pulsating companion is a massive white dwarf. Employing Eggleton＇s stellar evolution code with the optically thick wind assumption, we find that the hot subdwarf HD 49798 and its X-ray pulsating companion could produce a type Ia supernova （SN Ia） in future evolution. This implies that the binary system is a likely candidate of an SN Ia progenitor. We also discuss the possibilities of some other WD ＋ He star systems （e.g. V445 Pup and KPD 1930＋2752） for producing SNe Ia.

关键词： binaries close -- stars individual (HD 49798) -- stars evolution -- supernovae general -- white dwarfs

Stellar kinematics and populations out to 1.5 effective radii in the elliptical galaxy NGC 4636

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Research in Astronomy and Astrophysics 2011年第8期11卷 909-923页

作者： Shi-Bi PU zhan-wen Han National Astronomical Observatory/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China

We present high quality long slit spectra along the major and minor axes out to 1.5 effective radii of the massive galaxy NGC 4636 taken by the Hobby-Eberly Telescope. Using the Fourier Correlation Quotient method, we measured the stellar line-of-sight velocity distribution along the axes. Furthermore, six Lick/IDS indices （Hβ, Mgb, Fe5015, Fe5270, Fe5335, Fe5406） are derived from the clean spectrum. By comparing the measured absorption line strengths with the predictions of Simple Stellar Population （SSP） models, we derived ages, total metallicity and a abundance profiles of the galaxy. This galaxy presents old and [α/Fe] overabundant stellar populations. Indeed, using the SSP model, we obtained the broadband color profiles. The theoretical colors match well with the measured colors and present red sharp peaks at the galaxy center. The sharp peaks of the colors are mainly shaped by the high metallicity in the galaxy＇s center. Interestingly, the galaxy has steep negative metaUicity gradients, but the trend flattens outwards. This result likely suggests that the center and outer regions of the galaxy formed through different formation processes.

关键词： galaxy: elliptical and lenticular -- galaxy: abundances -- galaxy: kine- matic and dynamics -- galaxy: individual (NGC 4636)

Fitting formulae for the effects of binary interactions on lick indices and colors of stellar populations

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Chinese Journal of Astronomy and Astrophysics 2009年第2期9卷 191-204页

作者： Zhong-Mu Li zhan-wen Han Dali Uinversity Dali 671003 China National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China

More than about 50% of stars are in binaries, but most stellar population studies take single star stellar population （ssSSP） models, which do not take binary interactions into account. In fact, the integrated peculiarities of ssSSPs are different from those of stellar populations with binary interactions （bsSSPs）. Therefore, it is necessary to investigate the effects of binary interactions on the Lick indices and colors of populations in detail. We show some formulae for calculating the difference between the Lick indices and colors of bsSSPs, and those of ssSSPs. Twenty-five Lick indices and 12 colors are studied in this work. The results can be conveniently used for calculating the effects of binary interactions on stellar population studies and for adding the effects of binary interactions into present ssSSP models. The electronic data and fortran procedures in the paper can be obtained on request from the authors.

关键词： galaxies stellar content -- galaxies elliptical and lenticular, cD

DPHK： real-time distributed predicted data collecting based on activity pattern knowledge mined from trajectories in smart environments

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Frontiers of Computer Science 2016年第6期10卷 1000-1011页

作者： Chengliang WANG Yayun PENG Debraj DE wen-zhan SONG Key Laboratory of Dependable Service Computing in Cyber Physical Society Chongqing University Chongqing 400044 China College of Computer Science Chongqing University Chongqing 400044 China Department of Computer Science Georgia State University Atlanta GK 30303 USA

In this paper, we have proposed and designed DPHK （data prediction based on HMM according to activity pattern knowledge mined from trajectories）, a real-time distributed predicted data collection system to solve the congestion and data loss caused by too many connections to sink node in indoor smart environment scenarios （like Smart Home, Smart Wireless Healthcare and so on）. DPHK predicts and sends predicted data at one time instead of sending the triggered data of these sensor nodes which people is going to pass in several times. Firstly, our system learns the knowl- edge of transition probability among sensor nodes from the historical binary motion data through data mining. Secondly, it stores the corresponding knowledge in each sensor node based on a special storage mechanism. Thirdly, each sensor node applies HMM （hidden Markov model） algorithm to pre- dict the sensor node locations people will arrive at according to the received message. At last, these sensor nodes send their triggered data and the predicted data to the sink node. The significances of DPHK are as follows：（a） the procedure of DPHK is distributed; （b） it effectively reduces the connection between sensor nodes and sink node. The time complexities of the proposed algorithms are analyzed and the performance is evaluated by some designed experiments in a smart environment.

关键词： trajectory prediction sensor data mining wireless sensor networks smart environments hidden Markov model

Hydrogen and helium shell burning during white dwarf accretion

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Research in Astronomy and Astrophysics 2018年第5期18卷 111-118页

作者： Xiao Cui Xiang-Cun Meng zhan-wen Han Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae（SNe Ia） are believed to be thermonuclear explosions of carbon oxygen（CO） white dwarfs（WDs） with masses close to the Chandrasekhar mass limit. How a CO WD accretes matter and grows in mass to this limit is not well understood, hindering our understanding of SN Ia explosions and the reliability of using SNe Ia as a cosmological distance indicator. In this work, we employed the stellar evolution code MESA to simulate the accretion process of hydrogen-rich material onto a 1.0 M⊙CO WD at a high rate（over the Eddington limit） of 4.3 × 10^-7 M⊙yr^-1. The simulation demonstrates the characteristics of the double shell burning on top of the WD, with a hydrogen shell burning on top of a helium burning shell. The results show that helium shell burning is not steady（*** flashes）. Flashes from the helium shell are weaker than those in the case of accretion of helium-rich material onto a CO WD. The carbon to oxygen mass ratio resulting from the helium shell burning is higher than what was previously thought. Interestingly, the CO WD growing due to accretion has an outer part containing a small fraction of helium in addition to carbon and oxygen. The flashes become weaker and weaker as the accretion continues.

关键词： stars evolution - supernovae general - white dwarfs

Electrodeposition of Copper from Citrate Alkaline Solution Containing Polyethyleneimine(PEI)

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稀有金属材料与工程 2012年第S1期41卷 172-175页

作者： wen, zhan Na, Du Hu Lixin Ou Yanggui Wuhan Res Inst Mat Protect Wuhan 430030 Peoples R China Hubei Univ Technol Wuhan 430068 Peoples R China

Mechanism of citrate alkaline copper electrodeposition in presence of polyethyleneimine was *** by SEM,It's propitious to obtain fine and symmetrical copper film at wider current densities with *** analysis indicated copper deposits exhibited growth orientation of crystal face(111),which remained with parallel *** voltammograms results indicated that polyethyleneimine adsorbing preferentially at cathode high current density area could make a stronger inhibition on copper *** by chronoamperometry,it's showed that initial stage behavior of copper electrodeposition belonged to diffusion controlled and three-dimensional progressive nucleation.

关键词： alkaline copper electrodeposition polyethyleneimine surface morphology growth orientation progressive nucleation

Resin composition: An indicator of oil maturity as revealed by fourier transform ion cyclotron resonance mass spectrometry

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Petroleum Science 2023年第2期20卷 769-775页

作者： Tian Liang Zhao-wen zhan Guo-Xiang Wang Yan-Rong Zou State Key Laboratory of Organic Geochemistry Guangzhou Institute of GeochemistryGuangzhouGuangdong510640China CAS Center for Excellence in Deep Earth Science GuangzhouGuangdong510640China University of Chinese Academy of Sciences Beijing100049China

A pyrolysis experiment was carried out on a Dongying Depression kerogen sample to separate the resin from the oil. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with a positive-ion detector was used to detect the relative proportional changes in the compounds of the resin. During the whole pyrolysis experiment, the relative ratio of resin exceed 10% of the soluble component at each temperature point. Five compounds were detected from the resin: N1, N1O1, N1O_(2), O1, and O_(2). To research the changes in the proportions of the compounds during pyrolysis clearly, these five compounds were divided into three classes: N1, N1Ox, and Ox. The N1 class has the largest proportion in resin at the beginning of the pyrolysis, while Ox class has the least proportion. And the relationship between the number and the molecular mass of three classes compound was researched. With increasing maturity, the proportion of N1 and the N1Ox class decreased rapidly, while the Ox class increased slowly. Through researching these resin compounds, it was found that an inversion in the proportions of above three compounds appeared at the end of the oil window. At the same time, we found that the DBE and carbon number of resin compounds have changed obviously during the pyrolysis: the DBE increased, while the carbon number decreased significantly. And the details of the change of each compound have been researched. This research extends our knowledge of judging the maturity of crude oil during the pyrolysis through the characteristics of compounds in resin and provides the new index based on resin for the evaluation of thermal evolution stage and hydrocarbon generation capacity of source rocks.

关键词： Resin Pyrolysis FT-ICR MS Heteroatom compound Maturity DBE

The Effect of Method of Constructing the Mass Distribution on Single Stellar Populations

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Chinese Journal of Astronomy and Astrophysics 2005年第4期5卷 371-378页

作者： Feng-Hui zhang Li-Fang Li zhan-wen Han National Astronomical Observatories Yunnan Observatory Chinese Academy of SciencesKunming 650011

We use two methods of constructing the initial mass distribution, the traditional way and Monte Carlo simulation, to obtain integrated U - B, B - V,V-R and V-I colours and absorption-line indices defined by the Lick Observatory image dissector scanner （referred to as Lick/IDS）, for instantaneous burst solarmetallicity single stellar populations with ages in the range 1-15Gyr. We find that the evolutionary curves of all colours obtained by the traditional method are smoother than those by Monte Carlo simulation, that the U- B and B- V colours obtained by the two methods agree with one another, while the V - R and V - I colours by the traditional method are bluer than those by Monte Carlo simulation.A comparison of the Lick/IDS absorption-line indices shows that the variations in all the indices by the traditional method are smoother than that for the Monte Carlo simulation, and that all the indices except for TiO1 and TiO2 are consistent with those for the Monte Carlo simulation.

关键词： star: evolution - galaxies: star clusters- galaxies: stellar content

The surviving companions in type Ia supernova remnants

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Research in Astronomy and Astrophysics 2017年第8期17卷 69-80页

作者： li-qing chen xiang-cun meng zhan-wen han yunnan observatories chinese academy of scienceskunming 650216china key laboratory for the structure and evolution of celestial objects chinese academy of scienceskunming 650216china university of chinese academy of sciences beijing 100049china center for astronomical mega-science chinese academy of sciencesbeijing 100012china

The single-degenerate(SD)model is one of the most popular progenitor models of type Ia supernovae(SNe Ia),in which the companion star can survive after an SN Ia explosion and show peculiar ***,searching for the surviving companion in type Ia supernova remnants(SNRs)is a potential method to verify the SD *** the SN 1604 remnant(Kepler’s SNR),although Chandra X-ray observation suggests that the progenitor is most likely a WD+AGB system,the surviving companion has not been *** possible reason is rapid rotation of the white dwarf(WD),causing explosion of the WD to be delayed for a spin-down timescale,and then the companion evolved into a WD before the supernova explosion,so the companion is too dim to be *** aim to verify this possible explanation by carrying out binary evolution *** this paper,we use Eggleton’s stellar evolution code to calculate the evolution of binaries consisting of a WD+red giant(RG).We assume that the rapidly rotating WD can continuously increase its mass when its mass exceeds the Chandrasekhar mass limit(MCh=1.378 M_⊙)until the mass-transfer rate decreases to be lower than a critical ***,we obtain the final masses of a WD in the range 1.378 M_⊙ to 2.707 M_⊙.We also show that if the spin-down time is less than 10~6yr,the companion star will be very bright and easily observed;but if the spin-down time is as long as^10~7 yr,the luminosities of the surviving companion would be lower than the detection *** simulation provides guidance in hunting for the surviving companion stars in SNRs,and the fact that no surviving companion has been found in Kepler’s SNR may not be definite evidence disfavoring the SD origin of Kepler’s SN.

关键词： stars evolution—binaries symbiotic—supernovae individual(SN 1604,SN 1006)